1. Field of the Invention
Devices, systems, and methods consistent with the invention relate to a method and apparatus for adaptive GMAW short circuit frequency control.
2. Description of the Related Art
As is well know, welding requires the creation of a welding arc which is used to perform the welding operation. It is also known that to perform proper welding the welding arc must be stable. That is, for many welding operations, there is a need to maintain the voltage, current, and/or frequency of the welding arc to ensure that a proper weld is performed.
For many types of welding techniques, such as gas metal arc welding (“GMAW”), the arc pulse frequency is to be maintained relatively constant throughout the welding process, so as to ensure a proper weld is achieved. The welding voltage and/or current are often used to control the arc pulse frequency. That is, in a typical system, an operator must preset the welding voltage and/or current in an effort to obtain the desired welding arc performance, such as pulse frequency.
However, a problem exists because every welding operation is different and the differences can change the electrical properties of the current path such that the voltage and/or current settings need to be different from welding operation to welding operation. This requires the welder to adjust or tune the voltage and/or current settings based on their experience and “best guess” as to what the settings should be.
FIG. 1 shows an electrical circuit 100 which is indicative of a typical welding operation. The electrical current and voltage for the welding operation is provided from the welding power source 101. The current/voltage is directed from the power source 101 through the conductor 105 which is coupled with the welding gun (not shown). The gun provides the current/voltage to the welding electrode (not shown) to create the welding arc 107 between the electrode and a workpiece 103. The current/voltage passes through the work piece and is conducted back to the power source 101 via another conductor 109 which is connected to a negative terminal of the power source 101.
It is known that each conduction path within an electrical system (such as a welding circuit) has various electrical properties such as resistance and inductance which affect the current/voltage through the conduction path. However, during a welding operation these variables can change because the conduction paths are constantly changing during welding. For example, a typical welding operation requires the welding arc 107 to move along the workpiece 103. The movement of the arc 107 changes the distance between the arc 107 and where the negative conductor 109 is attached to the workpiece 103. The distance can either grow or decrease. This change in the distance causes a change in the electrical properties of the current path between the arc 107 and the negative conductor 109, through the workpiece 103. For example, the resistance can increase or decrease. Of course, other electrical variables can change.
Thus, these changes dynamically affect the performance of the welding operation and typically can not be adjusted “on the fly” or can not be properly taken into account when setting the initial voltage and/or current settings.
Additionally, the conductors 105 and 109 can affect the welding operation. That is, even though their properties typically do not change during a single welding operation, they may change between different welding operations. For example, it may be required for a welder to use a longer or shorter negative conductor 109. The change in length can change the resistance and/or impedance between welding operations.
Because of the foregoing, the welding process can change dynamically during the welding operation and between different welding operations. This requires a welder to carefully tune the voltage, current and/or frequency based on experience, feel and/or a best guess as to the proper settings. This imparts an amount of error into the welding operation. Further, because the current path properties change during welding the welding quality can decrease during welding even if the settings are properly set initially.
Accordingly, a need exists for a welding method and apparatus which addresses the above drawbacks of current welding systems.